The climate crisis is the focus of attention worldwide, while the second, equally threatening crisis usually receives less attention: the rapid loss of biodiversity. But as scientists are now emphasizing, both crises are closely linked - and therefore also require coordinated action. Because without climate protection, biodiversity will continue to decline, while a lack of species protection reduces the buffering effect of nature and increases climate change.
We humans have massively changed our planet and also intervened in the earth's energy balance and material flows. The consequence is global climate change, as a result of which the atmosphere and earth's surface continue to warm up, the distribution of precipitation shifts and extreme weather events increase. Sea levels are rising in the oceans, the water is becoming more and more acidic and zones of oxygen deficiency are spreading. "The climate crisis that he himself caused is probably the greatest challenge that Homo sapiens has had to face in its 300,000-year history," says Hans-Otto Pörtner from the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research.
Two crises in close interaction
But this is not the only man-made crisis on our planet: "At the same time, a second, equally threatening crisis is taking place, which often goes under - the drastic loss of animal and plant species all over the planet," says Pförtner. In an overview study, he and his team provide impressive figures on the ongoing loss of species. Accordingly, we humans have already changed around 75 percent of the land surface and 66 percent of the ocean areas. The loss of habitats and the destruction of natural ecosystems, in turn, has led to a decrease in the biomass of wild mammals by around 80 percent and that of plants by half. More species are threatened with extinction today than at any time in human history.
This biodiversity crisis is additionally intensified by climate change. "Both catastrophes - the climate crisis and the biodiversity crisis - cause and reinforce each other and should therefore by no means be viewed in isolation," explains Pförtner. On the one hand, climate change is depriving many species of their livelihoods: they have to follow the shift in climate zones in order to maintain the living conditions they need. However, many species are not mobile or adaptable enough – they are stuck in the temperature trap: Tropical corals, high mountain species or polar species have no alternative and are dying out. At the same time, warming is also reducing the carbon storage capacities of organisms, soils and, in turn, exacerbating the climate crisis.
It is only possible with coordinated action
According to Pförtner and his international team, the vicious circle that encompassed both crises can only be broken if coordinated measures focus on both the climate and species protection. Then there are considerable synergy effects: "Extensive renaturation of just 15 percent of the areas converted to farmland could be sufficient to prevent 60 percent of the extinction events that are still to be expected," explains the researcher. "At the same time, up to 300 gigatons of carbon dioxide could be removed from the atmosphere and bound in the long term, which corresponds to twelve percent of all carbon emitted since the beginning of the industrial age."
In order to counter the crises, the scientists propose an action package consisting of emission reduction, renaturation and protection measures and sustainable management of usable land. In addition to complying with the 1.5 degree target, they advocate that at least 30 percent of the earth's surface be placed under protection or renatured in order to avoid the greatest loss of biodiversity and to preserve the functionality of natural ecosystems. The nature reserves should not form isolated islands, but be made into a global network through migration corridors. In areas that we humans use intensively for agriculture or fishing, it is necessary to find new, resource-conserving forms of use that also lead to increased carbon sequestration in biomass and soil.
"However, all of this only works if climate protection, biodiversity conservation and social benefits for the local population are considered together in all the measures that have been decided on," says Pörtner. "The new global biodiversity, climate and sustainability goals planned for 2030 and 2050 will probably fail if the individual institutions do not work together more interdisciplinary." So far, two separate international agreements and separate conferences of the parties have regulated the protection of biodiversity and the climate. "We urgently need a holistic approach here if the goals are to be achieved," said Pförtner.
Source: Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research; Specialist article: Science, doi: 10.1126/science.abl4881